A technology has been proposed in which, for imaging a subject such as a document, a subject is irradiated with a white light and the light coming from the subject is imaged by a television camera (Patent reference 1). To obtain a high resolution color image by such a technology, it is necessary to arrange photodetecting elements for three primary colors (a photodetecting element for red color, a photodetecting element for green color and a photodetecting element for blue color) with high density in a television camera. This may bring a problem that the imaging apparatus becomes expensive.
On the other hand, a technology has been proposed, in which a subject is irradiated with a red light, a green light and a blue light at a delayed irradiation timing, and a line sensor is scanned while detecting the intensity of the light coming from the subject when the red light is irradiated, the intensity of the light coming from the subject when the green light is irradiated and the intensity of the light coming from the subject when the blue light is irradiated with a monochromatic photodetecting element, which is mounted in the line sensor (Patent reference 2). According to this technology, one photodetecting element corresponds to the three primary colors even for obtaining high resolution color image; thus, the fewest number of photodetecting elements is required.